Surface-modifiers of clay on mechanical properties of rigid polyurethane foams/organoclay nanocomposites

Natural Oil-Based Rigid Polyurethane Foam Thermal Insulation Applicable at Cryogenic Temperatures

This paper presents research into the preparation of rigid polyurethane foams with bio-polyols from rapeseed and tall oil. Rigid polyurethane foams were designed with a cryogenic insulation application for aerospace in mind. The polyurethane systems containing non-renewable diethylene glycol (DEG) were modified by replacing it with rapeseed oil-based low functional polyol (LF), obtained by a two-step reaction of epoxidation and oxirane ring opening with 1-hexanol. It was observed that as the proportion of the LF polyol in the polyurethane system increased, so too did the apparent density of the foam material. An increase in the value of the thermal conductivity coefficient was associated with an increase in the value of apparent density. Mechanical tests showed that the rigid polyurethane foam had higher compressive strength at cryogenic temperatures compared with the values obtained at room temperature. The adhesion test indicated that the foams subjected to cryo-shock obtained similar values of adhesion strength to the materials that were not subjected to this test. The results obtained were higher than 0.1 MPa, which is a favourable value for foam materials in low-temperature applications.

Studies on the thermal properties of poly(1,4-butylene terephthalate)/microencapsulated ammonium polyphosphate composites

This work aims to explore the potential of microencapsulated ammonium polyphosphate (MAPP) in poly(1,4-butylene terephthalate) (PBT). PBT/MAPP composites were prepared via melt blending method. The study of their thermal behaviors and thermal stability showed that the addition of MAPP with silica gel shell (MAPP(Si)) improved the relative crystallinity and thermal stability of PBT composites, in comparison with untreated ammonium polyphosphate and MAPP with polyurethane shell. Possible mechanisms for PBT/MAPP(Si) composites were investigated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. The results indicated that several PBT molecules may be grafted onto the surface of MAPP(Si), which improves the relative crystallinity and thermal stability of PBT/MAPP(Si) composites.

The Effect of Different Clay Dispersion Methods on the Properties of Polyurethane/Clay Nanocomposites

Polyurethane/clay (PU/clay) nanocomposites were synthesised using polymerisation and dispersion blending methods. The intercalation and exfoliation properties of the PU/clay nanocomposites were investigated by X-ray diffraction and transmission electron microscope. Clay intercalation of polymerised PU/nanocomposites was achieved and the interlayer spacing of clay was greatly enlarged from 17 Å to ~30 Å. Expansion in d-spacing was also observed for PU/clay nanocomposites prepared using dispersion methods. PU/clay nanocomposites prepared from dispersion of clay particles in the prepolymer matrix, followed by chain extension reaction, showed much high molecular weight and significant improvement in mechanical properties as compared with PU/clay nanocomposites produced using polymerisation or a simple high speed blending method in which clay was blended into the PU matrix. For PU/clay nanocomposites prepared using the blending method, high speed dispersion of 2 % clay in PU resulted in approximately a two-fold increase in the Young’s modulus. Further increase in the clay loading from 2 to 6 % made the corresponding nanocomposite polymer films more rigid and stiffer. This study shows that PU/clay nanocomposite properties are highly dependent on the preparation methods and provides useful guidelines for the future design and preparation of PU/clay nanocomposites.

Reactive Nanocomposite Foams

One of the most interesting and most accessible opportunities of nanofillers is the reinforcement of fine structures in which conventional fillers cannot be readily accommodated, such as polymer foams. This paper reviews the progress to date towards the development of reactive foam nanocomposites, in particular polyurethane and silicone foams. The discussed systems are summarized based on the types of nanofillers used, i.e. nanoparticles, rod-like, and plate-like systems. The effect of nanofillers on the foaming process, cellular structure and properties is critically reported along with a summary of the measured improvements in the mechanical, electrical and thermal properties of the resulting nanocomposites.